Benzoisothiazole azo dyestuffs

ABSTRACT

Azo dyestuffs of the formula ##STR1## wherein R 1  denotes hydrogen, C 1  -C 4  -alkoxy or C 1  -C 4  -alkoxyethoxy and 
     X denotes acyl, 
     are distinguished by good levelling properties and good allround fastness properties. They dye polyester fibres in a bright blue shade.

The invention relates to a disperse dyestuff of the formula ##STR2##wherein R₁ denotes hydrogen, C₁ -C₄ -alkoxy or C₁ -C₄ -alkoxyethoxy and

R₂ denotes hydrogen, C₁ -C₅ -alkyl, C₁ -C₅ -alkoxy, NH₂, NH--C₁ -C₅-alkyl, optionally CH₃ --, Cl--, OCH₃ -- or OC₂ H₅ -substituted phenyls,fur-2-yl, thien-2-yl or 3,4-pyrid-2-yl.

Preferred dyestuffs are those of the formula I wherein

R₁ denotes hydrogen or C₁ -C₂ -alkoxy and

R₂ denotes C₁ -C₄ -alkyl, in particular C₁ -C₂ -alkyl.

These dyestuffs are obtained in conventional manner by diazotisation andcoupling of appropriate starting materials.

The new dyestuffs have good levelling properties and high resistance toacids, alkali and redox systems and are therefore highly suitable fordyeing on synthetic fibre materials, in particular polyester andcellulose triacetate fibres, which are dyed in a bright, neutral orgreenish-blue shade.

The dyes obtained are distinguished by good allround fastness propertiesand the absence of the catalytic fading effect. Also noteworthy are thevery good wet fastness properties of the dyes on polyester/cottonarticles.

In comparison with similar dyestuffs as described in No. DE-A-1,544,375(=U.S. Pat. No. 3,455,898), there are distinct advantages in affinityand in wet fastness properties.

Compared with the structurally most comparable dyestuffs of No.DE-A-2,849,471 (=U.S. Pat. No. 4,465,628), the dyestuffs according tothe invention have better build-up properties in the presence of carrierand less temperature-dependent affinity.

It is particularly remarkable that the new azo dyestuffs, in thebrightness of their dyeings, come very close to similarly applied butsignificantly more costly anthraquinone dyestuffs, for example DisperseBlue 56 and Disperse Blue 73.

EXAMPLE 1

149 g of 3-amino-5-nitro-2,1-benzoisothiazole are added at 5° to 8° C.with stirring to a mixture of 350 ml of 96% strength sulphuric acid and125 ml of 85% strength orthophosphoric acid in the course of about 30minutes, and the mixture is stirred for a further 30 minutes. 132 ml ofnitrosylsulphuric acid are added dropwise at 3° to 5° C. The mixture issubsequently stirred at 3° C. for a total of 3 hours.

The resulting solution of the diazonium salt is then added to a solutionof 288.5 g of 3-[bis(2-methoxyethyl)-amino]-acetanilide, 7.5 g ofsulphamic acid and 5 g of emulsifier in a mixture of 2 l of water, 4 kgof ice and 168 ml of 48% strength sulphuric acid in the course of about30 minutes. The coupling is complete after 1 hour.

The dyestuff is then filtered off with suction and washed with water. Itdyes polyester fibres in a greenish-blue shade having good allroundfastness properties. A solution of the dried dyestuff indimethylformamide is characterised by λ max: 620 nm.

To prepare a modification which is stable to dyeing, the moist dyestuffpresscake is suspended in 6 l of water, and the suspension isneutralised (pH 7.5-8) with about 500 ml of sodium hydroxide solution(40 g of NaOH/100 ml). The suspension is heated with direct steam to 60°C. in the course of an hour and is heat-treated at 60°-70° C. for 4hours.

When the suspension has cooled down to 50° C., the dyestuff is filteredoff again with suction, is washed with water and is dried. The result is315 g of dyestuff which is characterised by the lattice plane spacingsd/Å 3.39, 3.49 and 4.18 having the relative intensities 100, 80 and 80respectively.

EXAMPLE 2

Example 1 is repeated, except that the coupling component is replaced byan equivalent amount of the compound of the formula ##STR3## and the pHestablished during the coupling with dilute NaOH is about pH 2.

The result is likewise a useful dyestuff which produces a blueish-greenshade on polyester fibres.

λmax (DMF): 654 nm.

We claim:
 1. An azo dyestuff of the formula ##STR4## wherein R₁ denoteshydrogen andR₂ denotes hydrogen or C₁ -C₂ -alkyl.
 2. An azo dyestuffaccording to claim 1, whereinR₁ denotes hydrogen and R₂ denotes methyl.3. A modification which is stable to dyeing of the dyestuff according toclaim 2, characterized by the lattice plane spacing d/Å 3.39, 3.49, 3.49and 4.18 having the relative intensities 100, 80 and 80 respectively.